<?php

/**
 * 3D Captcha text generator
 * (C) 2006 by Marc S. Ressl
 */

// Generate a 5-letter word that does not contain profane language:
session_start();
$_SESSION['3DCaptchaText'] = generateCaptchaTextMarkovClean(5);

// Generates a random word with uppercase/lowercase/number characters

function generateCaptchaTextRandom($length) {
	// Character list is fine tuned:
	// No 0-O-o
	$chars = 'abcdefghijklmnpqrstuvwxyzABCDEFGHIJKLMNPRSTUVWXYZ123456789';
	$n = strlen($chars);
	$captchaText = '';

	for ($i = 0; $i < $length; $i++) {
		$captchaText .= $chars[rand(0, $n - 1)];
	}

	return $captchaText;
}

// Generate a random word using a Markov chain.
// The transition matrix was calculated with Oscar Wilde's The Picture of Dorian Gray.
// Markov chains produce quite easy to type words.

function generateCaptchaTextMarkov($length) {
	$transitionMatrix = array(
	0.0001, 0.0218, 0.0528, 0.1184, 0.1189, 0.1277, 0.1450, 0.1458, 0.1914, 0.1915, 0.2028, 0.2792, 0.3131, 0.5293, 0.5304, 0.5448, 0.5448, 0.6397, 0.7581, 0.9047, 0.9185, 0.9502, 0.9600, 0.9601, 0.9982, 1.0000, 
	0.0893, 0.0950, 0.0950, 0.0950, 0.4471, 0.4471, 0.4471, 0.4471, 0.4784, 0.4821, 0.4821, 0.6075, 0.6078, 0.6078, 0.7300, 0.7300, 0.7300, 0.7979, 0.8220, 0.8296, 0.9342, 0.9348, 0.9351, 0.9351, 1.0000, 1.0000, 
	0.1313, 0.1317, 0.1433, 0.1433, 0.3264, 0.3264, 0.3264, 0.4887, 0.5454, 0.5454, 0.5946, 0.6255, 0.6255, 0.6255, 0.8022, 0.8022, 0.8035, 0.8720, 0.8753, 0.9545, 0.9928, 0.9928, 0.9928, 0.9928, 1.0000, 1.0000, 
	0.0542, 0.0587, 0.0590, 0.0840, 0.3725, 0.3837, 0.3879, 0.3887, 0.5203, 0.5208, 0.5211, 0.5390, 0.5435, 0.5550, 0.8183, 0.8191, 0.8191, 0.8759, 0.9376, 0.9400, 0.9629, 0.9648, 0.9664, 0.9664, 1.0000, 1.0000, 
	0.0860, 0.0877, 0.1111, 0.2533, 0.3017, 0.3125, 0.3183, 0.3211, 0.3350, 0.3355, 0.3378, 0.4042, 0.4381, 0.5655, 0.5727, 0.5842, 0.5852, 0.7817, 0.8718, 0.9191, 0.9201, 0.9530, 0.9652, 0.9792, 0.9998, 1.0000, 
	0.1033, 0.1037, 0.1050, 0.1057, 0.2916, 0.3321, 0.3324, 0.3324, 0.4337, 0.4337, 0.4337, 0.4912, 0.4912, 0.4912, 0.7237, 0.7274, 0.7274, 0.8545, 0.8569, 0.9150, 0.9986, 0.9986, 0.9990, 0.9990, 1.0000, 1.0000, 
	0.1014, 0.1017, 0.1024, 0.1028, 0.2725, 0.2729, 0.2855, 0.4981, 0.5770, 0.5770, 0.5770, 0.6184, 0.6191, 0.6384, 0.7783, 0.7797, 0.7797, 0.9249, 0.9663, 0.9688, 0.9923, 0.9923, 0.9937, 0.9937, 1.0000, 1.0000, 
	0.2577, 0.2579, 0.2580, 0.2581, 0.6967, 0.6970, 0.6970, 0.6970, 0.8648, 0.8648, 0.8650, 0.8661, 0.8667, 0.8670, 0.9397, 0.9397, 0.9397, 0.9509, 0.9533, 0.9855, 0.9926, 0.9926, 0.9929, 0.9929, 1.0000, 1.0000, 
	0.0324, 0.0478, 0.0870, 0.1267, 0.1585, 0.1908, 0.2182, 0.2183, 0.2193, 0.2193, 0.2309, 0.2859, 0.3426, 0.6110, 0.6501, 0.6579, 0.6583, 0.6923, 0.8211, 0.9764, 0.9781, 0.9948, 0.9949, 0.9965, 0.9965, 1.0000, 
	0.1276, 0.1276, 0.1276, 0.1276, 0.4286, 0.4286, 0.4286, 0.4286, 0.4337, 0.4337, 0.4337, 0.4337, 0.4337, 0.4337, 0.6684, 0.6684, 0.6684, 0.6684, 0.6684, 0.6684, 1.0000, 1.0000, 1.0000, 1.0000, 1.0000, 1.0000, 
	0.0033, 0.0059, 0.0100, 0.0109, 0.5401, 0.5443, 0.5477, 0.5485, 0.7149, 0.7149, 0.7149, 0.7316, 0.7333, 0.9247, 0.9264, 0.9273, 0.9273, 0.9289, 0.9791, 0.9816, 0.9824, 0.9824, 0.9833, 0.9833, 1.0000, 1.0000, 
	0.0850, 0.0865, 0.0874, 0.1753, 0.3439, 0.3725, 0.3744, 0.3746, 0.5083, 0.5083, 0.5192, 0.6784, 0.6840, 0.6848, 0.8088, 0.8128, 0.8128, 0.8147, 0.8326, 0.8511, 0.8743, 0.8817, 0.9054, 0.9054, 1.0000, 1.0000, 
	0.1562, 0.1760, 0.1774, 0.1776, 0.5513, 0.5517, 0.5517, 0.5520, 0.6352, 0.6352, 0.6352, 0.6369, 0.6486, 0.6499, 0.7717, 0.8230, 0.8230, 0.8337, 0.8697, 0.8703, 0.9376, 0.9376, 0.9378, 0.9378, 1.0000, 1.0000, 
	0.0255, 0.0265, 0.0682, 0.2986, 0.4139, 0.4204, 0.6002, 0.6009, 0.6351, 0.6360, 0.6507, 0.6672, 0.6679, 0.6786, 0.7718, 0.7723, 0.7732, 0.7873, 0.8364, 0.9715, 0.9753, 0.9797, 0.9803, 0.9804, 0.9997, 1.0000, 
	0.0050, 0.0089, 0.0183, 0.0379, 0.0410, 0.1451, 0.1494, 0.1514, 0.1654, 0.1656, 0.1866, 0.2171, 0.2821, 0.4272, 0.4761, 0.4926, 0.4927, 0.6434, 0.6722, 0.7195, 0.9126, 0.9332, 0.9913, 0.9925, 0.9999, 1.0000, 
	0.1596, 0.1688, 0.1688, 0.1688, 0.3799, 0.3799, 0.3799, 0.4011, 0.4827, 0.4827, 0.4833, 0.6081, 0.6087, 0.6090, 0.7353, 0.7953, 0.7953, 0.8804, 0.9181, 0.9584, 0.9952, 0.9952, 0.9952, 0.9952, 1.0000, 1.0000, 
	0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 0.0000, 1.0000, 1.0000, 1.0000, 1.0000, 1.0000, 1.0000, 
	0.0902, 0.0938, 0.1003, 0.1555, 0.4505, 0.4606, 0.4705, 0.4740, 0.5928, 0.5928, 0.6018, 0.6201, 0.6402, 0.6605, 0.7619, 0.7666, 0.7671, 0.8125, 0.8645, 0.9029, 0.9226, 0.9298, 0.9319, 0.9319, 0.9996, 1.0000, 
	0.0584, 0.0598, 0.0903, 0.0912, 0.2850, 0.2870, 0.2883, 0.3902, 0.5057, 0.5058, 0.5165, 0.5271, 0.5400, 0.5447, 0.6525, 0.6762, 0.6792, 0.6792, 0.7512, 0.9370, 0.9843, 0.9851, 0.9953, 0.9953, 0.9999, 1.0000, 
	0.0416, 0.0419, 0.0466, 0.0467, 0.1673, 0.1696, 0.1697, 0.6314, 0.7003, 0.7003, 0.7003, 0.7142, 0.7150, 0.7160, 0.8626, 0.8626, 0.8627, 0.9023, 0.9255, 0.9498, 0.9746, 0.9746, 0.9812, 0.9812, 0.9998, 1.0000, 
	0.0141, 0.0308, 0.0668, 0.0877, 0.1241, 0.1282, 0.1874, 0.1874, 0.2191, 0.2192, 0.2210, 0.3626, 0.3794, 0.4618, 0.4632, 0.5097, 0.5097, 0.6957, 0.8373, 0.9949, 0.9949, 0.9961, 0.9963, 0.9982, 0.9984, 1.0000, 
	0.0740, 0.0740, 0.0740, 0.0740, 0.8423, 0.8423, 0.8423, 0.8423, 0.9486, 0.9486, 0.9486, 0.9486, 0.9486, 0.9491, 0.9836, 0.9836, 0.9836, 0.9849, 0.9849, 0.9849, 0.9907, 0.9907, 0.9907, 0.9907, 1.0000, 1.0000, 
	0.2785, 0.2789, 0.2795, 0.2823, 0.4088, 0.4118, 0.4118, 0.6070, 0.7774, 0.7774, 0.7782, 0.7840, 0.7840, 0.8334, 0.9704, 0.9704, 0.9704, 0.9861, 0.9996, 1.0000, 1.0000, 1.0000, 1.0000, 1.0000, 1.0000, 1.0000, 
	0.0741, 0.0741, 0.1963, 0.1963, 0.2519, 0.2741, 0.2741, 0.3333, 0.4000, 0.4000, 0.4000, 0.4000, 0.4000, 0.4000, 0.4037, 0.6741, 0.7667, 0.7667, 0.7667, 0.9667, 0.9963, 0.9963, 0.9963, 0.9963, 1.0000, 1.0000, 
	0.0082, 0.0130, 0.0208, 0.0225, 0.1587, 0.1608, 0.1613, 0.1686, 0.2028, 0.2028, 0.2032, 0.2322, 0.2391, 0.2417, 0.8232, 0.8314, 0.8314, 0.8409, 0.9529, 0.9965, 0.9965, 0.9965, 0.9991, 0.9996, 1.0000, 1.0000, 
	0.0678, 0.0678, 0.0763, 0.0763, 0.7373, 0.7373, 0.7373, 0.7458, 0.8729, 0.8729, 0.8729, 0.8814, 0.8814, 0.8814, 0.9237, 0.9237, 0.9237, 0.9237, 0.9237, 0.9407, 0.9492, 0.9492, 0.9492, 0.9492, 0.9492, 1.0000
	);

	$chars = 'abcdefghijklmnopqrstuvwxyz';
	$captchaText = '';
	$char = rand(0, 25);

	for ($i = 0; $i < $length; $i++) {
		$captchaText .= chr($char + 65 + 32);

		// Look up next char in transition matrix
		$next = rand(0, 10000) / 10000;
		for ($j = 0; $j < 26; $j++) {
			if ($next < $transitionMatrix[$char * 26 + $j]) {
				$char = $j;
				break;
			}
		}

	}

	return $captchaText;
}

// The following section intercepts profane language
// generated by our captcha text generator.
//
// Please be warned that you are about to see a list of
// sensitive words that may hurt your sensibility.
// The purpose of this list is to filter these words from our
// Markov-chain character generator, in order to not insult the
// person using our captcha!

function generateCaptchaTextMarkovClean($length) {
	do {
		$cleanText = generateCaptchaTextMarkov($length);
	} while (
		// http://en.wikipedia.org/wiki/List_of_profane_words
		(preg_match('/anal/', $c) > 0) ||
		(preg_match('/anus/', $c) > 0) ||
		(preg_match('/arse/', $c) > 0) ||
		(preg_match('/bitch/', $c) > 0) ||
		(preg_match('/blow/', $c) > 0) ||
		(preg_match('/boner/', $c) > 0) ||
		(preg_match('/boob/', $c) > 0) ||
		(preg_match('/butt/', $c) > 0) ||
		(preg_match('/clit/', $c) > 0) ||
		(preg_match('/cock/', $c) > 0) ||
		(preg_match('/crap/', $c) > 0) ||
		(preg_match('/cum/', $c) > 0) ||
		(preg_match('/cunt/', $c) > 0) ||
		(preg_match('/dick/', $c) > 0) ||
		(preg_match('/dildo/', $c) > 0) ||
		(preg_match('/edema/', $c) > 0) ||
		(preg_match('/erect/', $c) > 0) ||
		(preg_match('/fag/', $c) > 0) ||
		(preg_match('/fart/', $c) > 0) ||
		(preg_match('/fuck/', $c) > 0) ||
		(preg_match('/hell/', $c) > 0) ||
		(preg_match('/hore/', $c) > 0) ||
		(preg_match('/jack/', $c) > 0) ||
		(preg_match('/jerk/', $c) > 0) ||
		(preg_match('/niger/', $c) > 0) ||
		(preg_match('/penis/', $c) > 0) ||
		(preg_match('/piss/', $c) > 0) ||
		(preg_match('/porn/', $c) > 0) ||
		(preg_match('/prick/', $c) > 0) ||
		(preg_match('/piss/', $c) > 0) ||
		(preg_match('/pubi/', $c) > 0) ||
		(preg_match('/pussy/', $c) > 0) ||
		(preg_match('/semen/', $c) > 0) ||
		(preg_match('/sex/', $c) > 0) ||
		(preg_match('/shag/', $c) > 0) ||
		(preg_match('/shit/', $c) > 0) ||
		(preg_match('/slut/', $c) > 0) ||
		(preg_match('/sperm/', $c) > 0) ||
		(preg_match('/suck/', $c) > 0) ||
		(preg_match('/tit/', $c) > 0) ||
		(preg_match('/wank/', $c) > 0) ||
		(preg_match('/whore/', $c) > 0)
		);

	return $cleanText;
}

?>
